This invention relates to an apparatus for controlling the dose of irradiation designed for controlling the dose of electron rays to be irradiated to a synthetic resin product such as a bottle or a film or its preform in order to eliminate the monomers contained in it as well as the dose of ultraviolet or infrared rays to be irradiated to such a product of surface treatment, material treatment or sterilization.
With an object of eliminating the monomers contained in synthetic resin products, their preforms are normally carried through an electron rays irradiation zone on a belt conveyer in a production line. A number of conveyers arranged in parallel may be arranged to pass through such an electron rays irradiation zone, each of the conveyers carrying products of a type which is different from those of the other conveyers.
With such an arrangement, the amount of electron rays to be irradiated to products should be differentiated depending on the thickness and shape of the products and other considerations. Such differentiation of dose of electron rays is normally realized by moving the belt conveyers at different speeds to optimize the duration of exposure to each products in the irradiation zone, the speed of each of the belt conveyers being appropriately selected to meet the required amount of electron rays for the preforms on it.
With a conventional apparatus for exposure of products to electron rays or other rays, the number of products that can be fed to a conveyer per unit time often differs from the number of products that can be treated by electron rays per unit time. Thus, such discrepancy results in congestion of products on belt conveyers and accidental fall of some of them from the conveyers, arising in trouble such as a poor productivity of the production line.
In other words, if a plurality of conveyers are installed within a production line, the number of products fed to each of the conveyers is a function of their size and shape while the speed at which each of the conveyers is operated is a function of the dose required by the products being carried on it and there are not any existing apparatuses that simultaneously satisfy these two functional requirements, entailing too poorly fed conveyers that operate at a high speed and too heavily fed conveyers that operate at a low speed and accompanied by the problem of congestion and occasional accidents.